Extenders for increasing the leverage of one-piece, relatively straight-handled wrenches are known, the most common probably being the ubiquitous length of pipe temporarily slid over the wrench handle.
More sophisticated examples include U.S. Pat. No. 5,570,617 to Love and U.S. Pat. No. 6,626,069 to Cooper.
The Love patent discloses an extendible extension handle for wrenches, ratchets, and tire irons to increase leverage, and uses a tubular inner handle and a telescoping outer handle assembly.
The Cooper patent discloses an angled adapter bar with a U-bolt for receiving the handle of a wrench, and a leverage bar for engaging the other end of the adapter bar, so that when all three are connected they multiply the force applied by the user to the wrench.
The foregoing prior art and other prior wrench extensions seem to focus on increasing leverage more than they address the problem of extending reach. In the case of nuts or bolts deeply recessed in tight places, reach is often the more important factor.